Effects of urease and nitrification inhibitors on the soil mineral nitrogen dynamics and nitrous oxide (N 2 O) emissions on calcareous soil

Abstract

Urease inhibitors and nitrification inhibitors can reduce nitrogen (N) loss in agriculture soil. However, the effect of inhibitors on soil N₂O emissions under the drip irrigation system remains unclear. A pot and a field experiment with two inhibitors were conducted to explore how inhibitors regulate soil nitrogen transformation and N₂O emissions. In the pot experiment, three treatments included control, urea, and urea + N-(n-butyl)thiophosphoric triamide (NBPT, urease inhibitor). In the field experiment, three treatments included control, urea, and urea + NBPT + 2-chloro-6-(trichloromethyl)pyridine (nitrapyrin, nitrification inhibitor). The urease inhibition rate in the treatment of urea + NBPT was 27.5% at the 14th day of incubation (pot experiment), and NH₄⁺-N was significantly decreased by 37–64% compared with urea alone treatment. In the field experiment, the nitrification inhibition rate in the treatment of urea + NBPT + nitrapyrin was 47.7 and 63.9% on the 3rd day after fertilization at the wheat heading and filling stages, respectively. Compared to urea treatment, NO₃⁻-N concentration in the double-inhibitor-added treatment was significantly decreased by 32 and 20% on the 5th day after fertilization at the heading and filling stages, respectively; N₂O fluxes were also decreased by 30.9 and 33.3% at the two stages of wheat, respectively. In total, adding an inhibitor reduced N loss by 7.39 and 7.44% at the 14th and 35th day in the pot experiment and by 10.53 and 6.65% at the two growing stages of wheat in the field experiment, respectively. Path and correlation analysis showed that N₂O emissions were significantly correlated with soil NO₃⁻ in both pot and field experiments.